by Elizabeth Weise and Melanie Eversley, USA TODAY

by Elizabeth Weise and Melanie Eversley, USA TODAY

A severe flu season prompted Boston Mayor Thomas Menino on Wednesday to declare a public-health emergency in the city.

Boston health officials have confirmed 700 cases of flu - 10 times the number for the entire flu season last year.

"This is the worst flu season we've seen since 2009, and people should take the threat of flu seriously," Menino said in a news release.

The Boston declaration is meant to drive home the message about the danger of flu and the necessity of getting vaccinated, said Nick Martin, communications director at the city Public Health Commission.

The city will offer free vaccinations this weekend.

"We're confident we have enough vaccine, and we're ordering more so we have surpluses on hand," Martin said.

Boston's Massachusetts General Hospital is seeing between 40 and 80 patients with flulike illnesses daily in its clinics and emergency department.

"This morning when we started the day at 6 a.m. we had over 50 patients waiting to be hospitalized in our emergency department and had many more patients waiting to be transferred in," chief nurse Jeanette Ives Erickson said. She couldn't say how many were flu patients but said the number was extraordinary.

Massachusetts has had 18 flu deaths so far this season, said Dave Kibby, a spokesman for the state Department of Public Health.

The hospitals in Boston have been overwhelmed, said Jim Heffernan, chief of primary care at Boston's Beth Israel Deaconess Medical Center. His hospital is full, he said, the emergency room "overflowing because there aren't enough places to put people. It just snowballs."

On Monday, Beth Israel got 400 more calls than normal to its urgent-care hotline, spokeswoman Kelly Lawman said. "We had to open a new unit to accommodate all the patients."

Although it's still early to say, Heffernan is concerned that this year's vaccine may not be as good a match for the circulating flu strains as originally hoped. Each year, vaccine manufacturers make an educated guess about the strains of flu likely to circulate worldwide. This year, the Centers for Disease Control and Prevention says the match is about 90%.

At Beth Israel, Heffernan said, several doctors and other staff members who were vaccinated came down with the flu. Still, he said, people should be vaccinated. "It's still protection," he said.

CDC's top doctor concurs. "The influenza vaccine is far from perfect but it is, by far, the best tool we have to prevent influenza, which remains a serious and potentially fatal disease," CDC Director Tom Frieden said.

Boston's mayor also urged people to get vaccinated.

"This is not only a health concern, but also an economic concern for families, and I'm urging residents to get vaccinated if they haven't already," he said. "It's the best thing you can do to protect yourself and your family." He added, "If you're sick, please stay home from work or school."

Flu cases accounted for more than 4% of all emergency-department visits at Boston hospitals this week, the mayor's office reported; 25% required hospitalization. Since Oct. 1, four Boston residents, all seniors, have died from flu-related illnesses, the mayor's office said.

In Chicago, Northwestern Memorial Hospital was one of eight hospitals that put out word they could not accept ambulances because their emergency rooms were inundated with flu patients and operating at capacity, said Rahul Khare, an emergency physician. Normally, no more than two hospitals in the area night be in that condition, he said.

"Over the last three to four days, we've had a pretty significant surge of patients coming in with flulike symptoms" including high fevers and body aches, Khare said."I'm surprised, because it's coming a little bit earlier than it usually does."

Many patients had underlying conditions such as diabetes or cancer, he said.

In Salisbury Township, Pa., Lehigh Valley Hospital-Cedar Crest normally admits 10 to 20 patients with influenza-like illness in a week at this time of year. After admitting more than 100 from Dec. 31 to Jan. 4, the hospital erected a tent.

At the surge tent, as it is called, flu patients who are not sick enough to be admitted can be treated more efficiently and quickly, said Terry Burger, a nurse who is director of infection control for the hospital's parent, the Lehigh Valley Health Network. "People with a milder illness â?¦ can be seen in a surge tent relatively quickly and then discharged."